Ontogenetic shift to more efficient locomotor morphology coincides with migration in anadromous alewife, Alosa pseudoharengus (Wilson, 1811) (Clupeomorpha; Alosidae)

Abstract Anadromous fishes experience different locomotory demands throughout their life cycle. We evaluated how functional locomotory traits change over ontogeny in anadromous Alosa pseudoharengus (Alewife). We found that as juveniles, a period in which predator avoidance, food acquisition and manoeuvring in complex environments are critical to survival, Alewife have traits conducive to higher turning performance. As adults, Alewife develop traits more conducive to sustained swimming, allowing them to efficiently swim in open waters and undergo upstream migration. This suggests that changing locomotory demands throughout an individual's life cycle can result in different optimal locomotor traits.